1. Field of the Invention
The present invention generally relates to devices for moving objects, and more particularly to a tray or table assembly for a patient transfer device wherein the table assembly includes upper and lower tables having counter-rotating, endless belts.
2. Description of the Related Art
A wide variety of products have been designed to move objects from one location to another and, in particular, transfer mobility-impaired individuals such as patients. In a hospital setting, patients must often be transported from their beds to an examination table or operating table, and back again. Basic devices for transferring patients include stretchers that are carried manually by two attendants, and wheeled gurneys that can more easily be handled by a single attendant.
There can still be problems, however, in getting a patient from a bed or other support surface onto a stretcher or gurney. If the patient is cooperative and not injured or disabled, it is a simple matter for the individual to slide over to the gurney with the assistance of a nurse, but if the patient is unconscious or has a disability or an injury (e.g., a broken bone) that might be worsened by movement, then great care must be taken in transferring the patient from the bed to the gurney. This problem is exacerbated when the patient is unusually heavy.
One solution to this problem is to slide a tray or sheet under the person and then, after the person is resting atop it, pull the tray or sheet off the bed and onto the gurney. A rigid tray can be forcibly inserted between the patient and the bed, and a sheet can be incrementally pushed under the person by first rocking him away from the gurney and then rocking back toward the gurney as the sheet is drawn under. This approach can still be difficult if the patient is uncooperative (i.e., unconscious), and can further be very uncomfortable even if the patient is cooperative, due to the frictional engagement of the tray with the body or the lack of firm support by the sheet.
Some transfer devices incorporate a rigid tray into the gurney that can move to the side and slide under a patient, and then slide back (while supporting the patient) to a centered position for transportation. In a further variation on this concept, the transfer device may use counter-rotating, endless belts to substantially eliminate friction against both the patient and the bed as support trays crawl under the patient. One example of such a design is shown in U.S. Pat. No. 5,540,321. A first endless belt surrounds a set of upper trays and a second endless belt surrounds a set of lower trays, so the portions of the belts that are in contact (between the upper and lower tray sets) move in the same direction at the same rate as they counter-rotate. As the trays are inserted under the patient, the belt on the upper tray everts outwardly at the same rate as the translational movement of the trays to crawl under the patient without introducing any significant friction, and the belt on the lower tray similarly everts along the bed sheet. Once the patient is supported by the trays, the entire tray assembly is raised off the bed and the device can be rolled on casters to transport the patient.
There are still several serious problems with the counter-rotating belt designs. The entire transfer device (including the base and support members) moves as the trays are inserted under the patient, and the base must extend under the bed or table in order to prevent the device from tipping over when the patient is carried (see, e.g., FIG. 10 of '321 patent). Because of this limitation, such devices cannot be used in all settings, i.e., wherein there is insufficient clearance space under the bed or table (a situation becoming more common as more accouterments are added to beds and tables that occupy the space underneath). These devices further only allow loading and unloading along one side of the device, which can present problems when the patient is not suitably oriented (head-to-feet) on the device with respect to the bed or table. Designs such as that shown in the '321 patent are also not particularly comfortable as there is only a thin layer of the belt interposed between the patient and the hard surface of the metal support trays. Moreover, hospitals are becoming increasingly concerned with potential contamination from patient fluids, and the prior art belt-type transfer devices are difficult if not impossible to properly clean.
Another problem relates to the initial impact of the trays as they acquire a patient. The height of the trays and the large diameter edge rollers in the '321 design present an abrupt bump along the patient's side during acquisition, and result in a similar bumpy delivery of the patient back to a support surface. The tray can be inclined, for example as shown in U.S. Pat. No. 4,914,769, but a large angle of inclination makes it more difficult to acquire the patient and can increase patient discomfort during loading and unloading. It is also more likely that a patient will roll off the table assembly if the edge portions can incline downward.
In light of the foregoing, it would be desirable to devise an improved patient transfer device that provided more flexibility in deployment while still being easy to operate and maneuver. It would be further advantageous if the device were more comfortable for the patient, yet could still maintain the patient in a stabilized manner during transport.